全新java初学者实践教程6(Java SE5.0版)
sH{4Y-J 基本语法3
06O2:5zF JMrEFk \NgYTZ 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
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[font="Times] 1.循环语句[font="Times]:while,do-while,for
,\_1w ,K9*%rW) [font="Times]2.分支语句[font="Times]:if-else,switch,
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' [font="Times]
lAb*fafQy 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
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O(fM?4w 4.异常处理语句[font="Times]:try-catch-finally,throw
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jf4 实践:
`uOT+B%R [font="Times] 1.循环语句
\MyLc/Gh5 [font="Times] while 语句
9s\A\$("l [font="Times]class While {
}>>1<P<8- [font="Times]public static void main(String args[]) {
'u *DA|HC [font="Times]int n = 10;
,:%CB"J [font="Times]while(n > 0) {
RRmz"j> [font="Times]System.out.println("tick " + n);
@.$| w>>T [font="Times]n--;
1eS&&J5 [font="Times]}
IpYM;tYw& [font="Times]}
e?0l" [font="Times]}
Q6PHpaj [font="Times] do…while 语句
[k.t WA,& [font="Times] class DoWhile {
cpL7!>^= [font="Times]public static void main(String args[]) {
'@o;-'b [font="Times]int n = 10;
q!.byrod [font="Times]do {
)
i;1*jK [font="Times]System.out.println("tick " + n);
~IYUuWF( [font="Times]n--;
+"rDT1^V [font="Times]} while(n > 0);
zQcL|(N [font="Times]}
_Gn2o2T [font="Times]}
Y~c|hfL 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
J\+0[~~ [font="Times] for语句
B^4&-z2| [font="Times] class ForTick {
[w0QZyUn [font="Times]public static void main(String args[]) {
|XQIfW]A [font="Times]int n;
'GNK "XA^ [font="Times]for(n=10; n>0; n--)
+ieY:H[ [font="Times]System.out.println("tick " + n);
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r [font="Times]}
6a[}'/ [font="Times]}
+O8%Hm 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
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UQ 还有啊,[font="Times]for循环的部分可以为空的
Vr]id [font="Times]class ForVar {
5eLtCsHz [font="Times]public static void main(String args[]) {
q
?|,O;? [font="Times]int i;
|cK*~ [font="Times]boolean done = false;
r+A{JHnN [font="Times]i = 0;
Vc 1\i [font="Times]for( ; !done; ) {
00(on28b [font="Times]System.out.println("i is " + i);
7?#J~.d5 [font="Times]if(i == 10) done = true;
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: [font="Times]i++;
3eb%OEMYk [font="Times]}
Si_ _8D [font="Times]}
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循环语句的例子下载 sd*p/Q|4 [font="Times] 2.分支语句[font="Times]
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N6+@ [font="Times] if/else语句
6.sx?Y YM [font="Times]class IfElse {
i+A3~w5c [font="Times]public static void main(String args[]) {
~-ia+A6GIV [font="Times]int month = 4; // April
umjt]Gu[ [font="Times]String season;
}q_<_lQ [font="Times]if(month == 12 || month == 1 || month == 2)
2M.fLQ? [font="Times]season = "Winter";
Ur9?Td'*> [font="Times]else if(month == 3 || month == 4 || month == 5)
D9<!mH [font="Times]season = "Spring";
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[font="Times]else if(month == 6 || month == 7 || month == 8)
NSxoF3 [font="Times]season = "Summer";
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. [font="Times]else if(month == 9 || month == 10 || month == 11)
H=<S 9M [font="Times]season = "Autumn";
ND'E8Ke pq [font="Times]else
BL0 {HV! [font="Times]season = "Bogus Month";
caIL&G, [font="Times]System.out.println("April is in the " + season + ".");
Z-^LKe [font="Times]}
Y1OCLnK~ [font="Times]}
(7vF/7BZ|_ [font="Times]//这段程序输出[font="Times]:
HHA<IZ#;, [font="Times]//April is in the Spring.
52%2R]G! [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
vmU@^2JSJ [font="Times] switch语句
Z?6%;n^ 54 [font="Times] class Switch {
@3) (BpFe [font="Times]public static void main(String args[]) {
qyZ"
%Kz [font="Times]int month = 4;
=b%MXT [font="Times]String season;
1a?!@g) [font="Times]switch (month) {
O9G[j=U [font="Times]case 12:
}u\])I3 [font="Times]case 1:
$:8x(&+/@ [font="Times]case 2:
V\>K]mwD [font="Times]season = "Winter";
ap.K=-H [font="Times]break;
b LB:MW\% [font="Times]case 3:
vUN22;Z\ [font="Times]case 4:
%P<hW+P! [font="Times]case 5:
{>}!+k
-` [font="Times]season = "Spring";
aT{_0m$G10 [font="Times]break;
v|gw9 [font="Times]case 6:
r A`V}>Xj [font="Times]case 7:
CnU*Jb [font="Times]case 8:
uW=k K0E [font="Times]season = "Summer";
o
m^0}$V [font="Times]break;
]3x? [font="Times]case 9:
\9cbI3rGz [font="Times]case 10:
HguT"%iv [font="Times]case 11:
_>5(iDW0 [font="Times]season = "Autumn";
Vp#JS3Y [font="Times]break;
E-4b[xNj*+ [font="Times]default:
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[font="Times]season = "Bogus Month";
|ax3sAg [font="Times]}
sGi"rg# [font="Times]System.out.println("April is in the " + season + ".");
S
^"y4-2 [font="Times]}
];VA!++ [font="Times]}
分支语句代码下载 Q!o'}nA -C;^3R[
O [font="Times]switch语句适合于条件非常多的逻辑
m!gz3u]rN 请看上述语句可以混合使用,请看
下载例子